This disclosure relates in general to content delivery over the Internet and, but not by way of limitation, to content delivery networks amongst other things.
Content delivery networks (CDNs) have a geographically distributed network of points of presence (POPs) such that one is likely to be close to an end user. A request for content is matched to a nearby POP using routing, domain name service (DNS) diversion, redirection, Anycast and/or other techniques. An edge server in the POP generally serves the content from a cache of the edge server, a host within the CDN, or an origin server depending on where the content is located. For content that is missing from the CDN, the request to the origin server can be costly in terms of quality of service (QoS). QoS can also be impacted by dropped packets and the associated delay, including due to the retransmission of packets.